Which of these numbers is composite? ${29,\ 37,\ 41,\ 69,\ 89}$
Solution: A composite number is a number that has more than two factors (including 1 and itself). 29, 37, 41, and 89 each have only two factors. The factors of 69 are 1, 3, 23, and 69. Thus, 69 is the composite number.